U.S. patent application number 12/999013 was filed with the patent office on 2011-04-28 for luminescence concentrators and luminescence dispersers on the basis of oriented dye zeolite antennas.
This patent application is currently assigned to Gion Calzaferri. Invention is credited to Christophe Bauer, Dominik Bruhwiler, Gion Calzaferri, Andreas Kunzmann.
Application Number | 20110094566 12/999013 |
Document ID | / |
Family ID | 39711811 |
Filed Date | 2011-04-28 |
United States Patent
Application |
20110094566 |
Kind Code |
A1 |
Calzaferri; Gion ; et
al. |
April 28, 2011 |
Luminescence Concentrators and Luminescence Dispersers on the Basis
of Oriented Dye Zeolite Antennas
Abstract
A luminescence concentrator (LK) may concentrate both incident
direct and diffuse light by way of frequency shift and total
internal reflection. It differs fundamentally from geometric
concentrators. With sufficient geometric expansion of the collector
plate, nearly arbitrarily high concentration can be achieved in the
LK. A luminescence disperser is an apparatus which holds both
directional and nondirectional incident light captive in a
transparent body by way of frequency shift and total internal
reflection and emits it diffusely or directionally uniformly
distributed across an area by way of luminescence emission. The
object of the invention is a method for the technical
implementation of the LK and luminescence disperser, using zeolite
crystals having a nanotube structure, into which the luminescent
dyes are embedded such that they have antenna properties. Using the
resulting novel structures, problems can be solved which made the
technical use of LK impossible or at least considerably limited it.
This results in completely novel usage possibilities for collecting
and concentrating sun light and feeding it into photovoltaic
systems, for converting it into electric and thermal energy in
combined photovoltaic/hot water apparatuses, and for feeding it
into fiber optic apparatuses.
Inventors: |
Calzaferri; Gion;
(Bremgarten, CH) ; Kunzmann; Andreas; (Staufen,
CH) ; Bruhwiler; Dominik; (Zurich, CH) ;
Bauer; Christophe; (Zurich, CH) |
Assignee: |
Calzaferri; Gion
Bremgarten
CH
Kunzmann; Andreas
Staufen
CH
UNIVERSITAT ZURICH
Zurich
CH
|
Family ID: |
39711811 |
Appl. No.: |
12/999013 |
Filed: |
March 31, 2009 |
PCT Filed: |
March 31, 2009 |
PCT NO: |
PCT/CH09/00074 |
371 Date: |
December 14, 2010 |
Current U.S.
Class: |
136/247 ;
126/698; 385/141; 427/157 |
Current CPC
Class: |
H01L 31/055 20130101;
Y02E 10/52 20130101; H01L 51/447 20130101; H01L 31/02322 20130101;
C09K 11/06 20130101; Y02P 70/50 20151101; Y02E 10/549 20130101;
Y02P 70/521 20151101; F24S 23/11 20180501 |
Class at
Publication: |
136/247 ;
385/141; 427/157; 126/698 |
International
Class: |
H01L 31/052 20060101
H01L031/052; G02B 6/00 20060101 G02B006/00; B05D 5/06 20060101
B05D005/06; F24J 2/08 20060101 F24J002/08 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 1, 2008 |
CH |
01016/08 |
Claims
1-13. (canceled)
14. A device for concentrating light, as a luminescence
concentrator, or dispersing light, as a luminescence disperser,
consisting of luminescent sites, which are formed from dye
molecules in supramolecular arrangement and organized in zeolites
so as to result in an antenna function, which luminescent sites are
referred to as antennas, which are embedded as one layer, or two or
more layers spaced apart, into a polymer and which are on or
between transparent sheets which are suitable for total internal
reflection and consist of glass, plastic or a combination thereof,
wherein the thickness of the sheets is of the order of magnitude of
one or more of these layers.
15. The device according to claim 14, wherein said device comprises
three regions in the sequence specified: transparent glass, plastic
or a combination thereof with refractive index n.sub.1 and sheet
thickness x.sub.1, on which the light is incident, one or more
directed dye-zeolite layers which consist of the light-absorbing
and light-emitting antennas, transparent glass, plastic or a
combination thereof with refractive index n.sub.2 and sheet
thickness x.sub.2.
16. The device according to claim 15, wherein the individual
dye-zeolite layers typically have a thickness between 100 nm and
2000 nm; the individual layers immediately adjoin one another or
are separated by intermediate layers of a transparent material
which are thin relative to the thickness of the sheets; the
refractive indices of the intermediate layers and of the polymer
into which the dye-zeolite layers are embedded are selected such
that a maximum light yield is ensured.
17. A process for producing a device for concentrating light as a
luminescence concentrator or dispersing light as a luminescence
disperser according to claim 14, wherein said device is produced by
an alternating application, repeatable as often as desired, of
transparent glass, plastic or a combination thereof, and one or
more dye-zeolite layers under the formation of stacks, the
distances between the individual dye-zeolite layers being
determined by the thickness of the intermediate layers, and these
dye-zeolite layers having different structures as a function of
different dye molecules, of the thickness of the dye-zeolite layers
and of the relative alignment of the zeolite crystals.
18. Method of use of a device according to claim 14 for
concentrating light as a luminescence concentrator, comprising the
steps of concentrating the light incident on the surface thereof,
both in diffuse and direct form, due to the frequency shift and
total internal reflection caused by antennas, and transferring said
concentrated light to one, more than one or all side surfaces of
the luminescence concentrator.
19. Method of use of a device according to claim 14 for dispersing
light as a luminescence disperser, comprising the step of emitting
light which is incident on one, more than one or all side surfaces
of the luminescence disperser, both in diffuse and direct form, on
the surface of the disperser or parts thereof as a result of the
frequency shift and total internal reflection caused by
antennas.
20. Method of use of a device according to claim 14 as a
luminescence concentrator, comprising the step of collecting and
concentrating sunlight and feeding it into photovoltaic energy
conversion systems.
21. Method of use of a device according to claim 14 as a
luminescence concentrator, comprising the step of collecting and
concentrating sunlight and feeding it into fiber optics
devices.
22. Method of use of a device according to claim 14 as a
luminescence concentrator, comprising the step of collecting and
concentrating sunlight and feeding it into photovoltaic energy
conversion tandem solar cells for increasing the electrical energy
yield.
23. Method of use of a device according to claim 14 as a
luminescence concentrator, comprising the step of collecting and
concentrating sunlight and feeding it into combined photovoltaic
hot water devices for the conversion of light to electrical and
thermal energy.
24. Method of use of a device according to claim 14 as a
luminescence concentrator, comprising the step of collecting
electromagnetic or particle radiation and converting it to light,
correspondingly to the way scintillation counters work, and
transporting it to a luminescence detector.
25. Method of use of a device as claimed in claim 14 as a
luminescence disperser, comprising the step of applying said device
for signaling systems, illuminated signage, room lighting,
flat/diffuse light sources and background illumination.
26. Method of use of a device as claimed in claim 14 as a
luminescence disperser, comprising the step of obtaining locally
directed emission for three-dimensional imaging in ophthalmology.
Description
TECHNICAL FIELD
[0001] The subject of the invention is a device for concentrating
as a luminescence concentrator or for dispersing as a luminescence
disperser as claimed in claim 1, a process for production thereof
as claimed in claim 4 and use thereof as claimed in claims 5, 6, 7,
8, 9, 10, 11, 12, 13.
STATE OF THE ART
[0002] A luminescence concentrator, which we abbreviate to LC
hereinafter, is a device which can concentrate both incident direct
and diffuse light by frequency shifting and total internal
reflection; see FIG. 1. These concentration processes differ
fundamentally from geometric concentrators. There is no limitation
by Liouville's theorem, according to which the product of photon
flux density and divergence of radiative flux always remains
constant in a geometric concentrator. Given sufficient geometric
dimensions of the collector plate, it is possible in principle in
the LC to achieve an almost unlimited concentration; on this
subject, see, for example, R. A. Garwin, Rev. Sci. Instr. 1960, 31,
1010; A. Goetzberger and V. Wittwer. Sonnenenergie, Teubner
Studienbucher Physik, ISBN 3-519-03081-0, Verlag Teubner 1986; W.
H. Weber, J. Lambe, Appl. Opt. 1976, 15, 2299; A. Goetzberger, W.
Greubel, Appl. Phys. 1977, 14, 123; J. S. Batchelder, A. H. Zewail,
T. Cole, Appl. Opt. 1979, 18, 3090; J. S. Batchelder, A. H. Zewail,
T. Cole, Appl. Opt. 1981, 20, 3733; R. Koeppe, N. Sariciftci, A.
Buchtemann, Appl. Phys. Lett. 90 (2007) 181126; P. Kittidachachan,
L. Danos, T. J. J. Meyer, N. Alderman, T. Markvart, Chimia, 2007,
61, 780.
[0003] An inverted luminescence concentrator, which we abbreviate
to iLC hereinafter, is a device which traps both directed and
undirected incident light by frequency shifting and total internal
reflection in a transparent body (for example glass or plastic) and
emits it, i.e. couples it out of the body, in a diffuse or directed
manner in homogeneous distribution over a surface by means of
luminescent emission. An iLC can thus function as a luminescence
disperser.
[0004] The significant problems with the LCs now known are: (A) the
loss which occurs as early as the first emission because total
internal reflection is limited by half the cylinder opening angle;
(B) intrinsic absorption with subsequent re-emission, which in turn
results in the same loss as (A), and which additionally proceeds
with a yield of a little less than 100%; (C) the necessity to
distribute (dissolve) the chromophores within a relatively thick
layer of several millimeters, which means a considerable
restriction for the optimization of the optical properties of the
LC, and more particularly makes it impossible or at least
considerably more difficult to build up materials of different
refractive index in a structured manner; (D) the stability of the
dyes which are generally dissolved in a polymer and are thus also
exposed to plasticizers and other reactive species and can even
migrate in the case of considerable temperature variations. These
are problems which considerably limit or even put into question the
efficiency, lifetime and flexibility--in the building of
arrangements, functional units or apparatuses--and hence the range
of use or even the usability of LCs; see the references given
above.
[0005] The significant problem with the uses now known, based on
light scattering, is homogeneous light emission over a relatively
large area, i.e. homogeneously distributing the light emission
intensity over an area. This is required, for example, for
background illumination in LCDs. Background illumination is used
for backlighting of LC displays (LCDs) of electronic units.
Examples are digital instruments, cellphones or flat visual display
units of televisions and monitors. In LCDs, this achieves an
increase in contrast compared to the non-self-illuminating, purely
reflective mode of operation. The purpose of background
illumination is to illuminate the visual display unit from the
rear, in a flat, homogeneous and efficient manner. The color of the
light source must be white in the case of color visual display
units (the individual color pixels of the LCDs allow the particular
color thereof to pass through), whereas it may be selected as
desired in monochrome displays. The light source must not flicker
in order to prevent superimpositions or beats with the actuation of
the display elements or pixels.
[0006] The light-emitting diodes are still very expensive as light
sources in relation to their lighting intensity. They are used for
background illumination in particular where their advantages--high
efficiency, long lifetime, robustness and small dimensions--are
particularly beneficial. A typical example is that of visual
display units for small mobile units such as cellphones or
navigation systems. LCD televisions equipped with LEDs are
commercially available, but have to date (2008) not achieved wide
acceptance. The most frequently used inexpensive light sources are
luminophore tubes (in the case of large displays, usually cold
cathode tubes). The UV radiation thereof is blocked by use of
specific tube glass in order not to damage the surrounding plastic.
Cold cathode tubes can be found in virtually all laptops, monitors,
LCD televisions and some PDAs.
[0007] Light sources which appear particularly suitable for use as
background illumination are those which are fundamentally flat
radiators, because this significantly reduces the demands on the
guiding of light. Since as early as about 1950 there have been
electroluminescent films which are extremely flat with thicknesses
of less than 1 mm. The efficiency, the lifetime and the achievable
luminance of electroluminescent films are, however, such that use
in monitors or televisions is impossible. Also implementable as
flat radiators are xenon low-pressure lamps with dielectric
hindrance of discharge (e.g. Planon from OSRAM) and organic
light-emitting diodes (OLEDs). These could become commercially
successful within a few years as soon as the efficiency and the
lifetime meet market demands. Incandescent lamps are no longer used
for backlighting.
[0008] The light emitted from point or linear light sources must be
distributed very substantially homogeneously over the area of the
background illumination. This is referred to as light guiding. In
the case of relatively weak background illumination, the light is
usually fed to the ends of a light conductor. In practise, the
light conductor is a flat sheet of a transparent plastic, for
instance acrylic glass. This contains extractors which emit the
light from the light conductor. The emission can be achieved by
scattering structures distributed in the light conductor material,
by specific fine surface structures, or by fine printed patterns.
The inhomogeneous distribution of the emitting structures has the
effect that the homogeneous illumination of the surface is also
achieved, for example, with only one cold cathode tube incident at
the end. To increase the luminance, the light sources may, however,
be mounted at two or all four end faces. Background illumination
according to this principle is referred to as "edge-lit
backlighting". With increasing size of the light source (and
constant side ratio, e.g. 16:9), the sum of the side lengths
increases only proportionally to the length of one side, but the
area increases as the square. Since the power or the efficiency of
the light sources cannot be enhanced to an unlimited degree, the
"edge-lit backlights" are fundamentally limited here. For larger
formats, constructions derived from the known light boxes are
therefore being used. The light sources in this case are in a flat
trough which reflects the light diffusely in the interior thereof
and only allows it to leave toward the open side. Specially shaped
reflectors are often used for luminophore lamps, and diffuser
lenses for LEDs, in order that the light exiting from the light
trough is approximately homogeneous in spite of a small
installation depth of the background illumination.
[0009] The light distributed by the light conductor or the light
trough possibly still has a spatial structure and has to be
distributed homogeneously with the aid of a diffuser in order that
it approximates to an absolutely homogeneously white-illuminating
surface. A simple solution is an opalescent scattering sheet
between light conductor or light trough and LC visual display unit.
It is usual, however, to use films which homogenize the light more
efficiently than is possible with opalescent glass. 3M, for
example, has developed the Vikuiti films which better exploit the
light by a factor of two compared to an opalescent diffuser. These
films reflect all that light which is unsuitable for the
backlighting of the LCD in respect of direction and polarization
back to the light conductor. This light is scattered within the
light conductor, mixed in terms of direction and polarization, and
goes back in the direction of the LCD. Similarly to a geometric
series, the operation is repeated and leads to better exploitation
of the light.
[0010] Especially the emission of the light from a light-conducting
material is nowadays realized with solutions for diffuse light
scattering. This can be achieved by means of scattering structures
which are distributed in the light conductor material, by means of
specific fine surface structures or by means of fine printed
patterns. To solve this problem, according to the present state of
the art, diffuse light scattering at rough surfaces is thus
employed, or a flat radiator is used (e.g. luminophore tubes).
These methods prevent the possibility of implementing the
illuminated surface transparently and as a homogeneous light
radiator; problem (E).
[0011] This problem (E) is solved by, instead of emission by
scattering, effecting emission by means of luminescence using an
iLC, since this can be made transparent. With the aid of the iLC
presented here, principles analogous to those for the luminescence
concentrator (LC) apply.
[0012] Over the course of several years, we have developed
processes which allow the construction of luminescent materials
with considerable optically anisotropic properties, in which
radiationless energy transfer from donor molecules to acceptors,
which then emit the light again as the luminescence, can be finely
adjusted such that a varied spectrum of interesting properties is
developed. Review articles which also illustrate the development of
this work are: G. Calzaferri, CHIMIA 52 (1998) 525-532; G.
Calzaferri, D. Bruhwiler, S. Megelski, M. Pfenniger, M. Pauchard,
B. Hennessy, H. Maas, A. Devaux, U. Graf, Solid State Sciences 2
(2000) 421-447; G. Calzaferri, S. Huber, H. Maas, C. Minkowski
Angew. Chem. Int. Ed. 42, 2003, 3732-3758; G. Calzaferri, K.
Lutkouskaya, Photochem. Photobiol. Sci., 2008, 7, 879-910.
[0013] We have already made earlier proposals that it would be
worth using the dye-zeolite materials that we developed for LCs; on
this subject see, for example: Orientierte Zeolith L Kristalle auf
einem Substrat, G. Calzaferri, A. Zabala Ruiz, H. Li, S. Huber,
Oriented zeolite material and method for producing the same,
PCT/CH2006/000394; priority U.S. 60/698,480 and CH 1266/05.
Nanochannel Materials for Quantum Solar Energy Conversion Devices,
D. Bruhwiler, L.-Q. Dieu, G. Calzaferri, CHIMIA, 61, 2007, 820-822.
Dye modified nanochannel materials for photoelectronic and optical
devices, G. Calzaferri, H. Li, D. Bruhwiler, Chem. Eur. J., 2008,
14, 7442-4749. In these studies, certain aspects of the new
materials which could be useful for the production of LCs are
discussed.
[0014] We have found, more particularly, that it is possible to
bind zeolite crystals into a polymer in such a way that the light
scattering caused by the zeolite crystals can be completely
suppressed within the relevant longer-wave range; on this subject,
see: Transparent Zeolite-Polymer Hybrid Materials with Tunable
Properties, S. Suarez, A. Devaux, J. Bannuelos, O. Bossart, A.
Kunzmann, G. Calzaferri, Adv. Funct. Mater. 17, 2007, 2298-2306;
Transparent Zeolite-Polymer Hybrid Material with Tunable
Properties, G. Calzaferri, S. Suarez, A. Devaux, A. Kunzmann, H. J.
Metz, PCT European Patent application EP1873202.
[0015] Important terms such as zeolite L, antenna, organized
dye-zeolite materials, etc. are explained in the study published in
German language: Photon-Harvesting Host-Guest Antenna Materials
(Wirt-Gast Antennenmaterialien) Gion Calzaferri, Stefan Huber, Huub
Maas, Claudia Minkowski, Angew. Chem. 115, 2003, 3860-3888; Angew.
Chem. Int. Ed. 42, 2003, 3732-3758. In FIG. 2, we show a
cylindrical zeolite nanocrystal with organized dye molecules, which
function as donors (grey rectangles) and acceptors (black
rectangles). In the left-hand part of the figure, the donors are in
the middle regions and the acceptors are at the two ends of the
channels; in the right-hand part, the donors are located at the
ends and the acceptors in the middle part. The dye molecules which
are ordered supramolecularly and organized in such a way in
zeolites are formed so as to result in an antenna function, which
luminescent sites are referred to as antennas. This achieves a
significant shift in the luminescence to greater wavelengths. The
enlargement shows details of a channel with a dye molecule whose
electronic transition moment (double-headed arrow) is parallel to
the channel axis in large molecules and deflected in smaller
molecules. The diameter of a channel opening of zeolite L is 0.71
nm, with a greatest channel diameter of 1.26 nm. The distance from
the middle of a channel to the middle of a neighboring channel is
1.84 nm.
DESCRIPTION OF THE INVENTION
[0016] The concept of the present study originated from the KTI
project 9231.2 PFNM-NM (development of efficient LCs based on
inorganic-organic nanomaterials for use in solar power generation).
It is an object of the invention to realize the individual
solutions to problems A) to D) in a new and integral manner in one
device. This enables a functioning and highly efficient LC. Taking
account of problem solution E), the result is even an iLC; see also
claims 1 and 4. Accordingly, the invention consists in using the
solutions to the abovementioned problems (A) to (E) with LCs and
iLCs by refined and rigorous exploitation of all research results
known to date, such that LCs and iLCs become of interest for
commercial utilization. This gives rise to new uses which are
described in some examples; see also claims 5 to 13.
[0017] The light-absorbing and light-transporting part consists
essentially of three regions and is shown schematically in FIGS. 1,
4 and 5. (B1) A transparent glass or polymer with refractive index
n.sub.1 and layer or sheet thickness x.sub.1, onto which the light
is incident. (B2) A light-absorbing and light-emitting part, which
we refer to as antenna and which works as explained in FIG. 2,
consisting of one or more, generally aligned dye-zeolite layers
(see FIG. 3) embedded into a transparent polymer. The thickness of
the individual zeolite layers is typically in the range between 100
nm and 2000 nm. The length and thickness of the zeolite crystals
used is likewise within this size range, disk-shaped crystals
frequently being advantageous. The individual layers may be very
tightly packed, or they may be separated via thin intermediate
layers of a transparent material. The refractive index of the
intermediate layers and of the polymer into which the zeolite
layers are embedded is selected so as to result in optimal
properties. (B3) Next follows a transparent polymer or glass with
refractive index n.sub.2 and layer or sheet thickness x.sub.2.
While the regions (B1) and (B3) meet customary requirements, are
typically a few mm thick and can also be formed, for example, from
two layers or sheets, for example a base body and a surface-treated
layer or sheet or a glass part and a polymer part, the region (B2)
is of more complex structure and constitutes the actual core piece;
see FIGS. 4 and 5. FIG. 4 shows a luminescence concentrator having
a dye-zeolite antenna layer. This antenna layer consists of one or
more layers of aligned or unordered dye-zeolite crystals embedded
in a thin polymer film, or coated with a thin polymer film. One of
the two immediately adjacent layers or sheets, with thickness
x.sub.1 or x.sub.2, can be omitted if required. The refractive
indices of the adjacent layers or sheets are n.sub.1 and n.sub.2;
n.sub.s is the refractive index of the antenna layer and n.sub.0 is
the refractive index of the environment (typically air).
.delta..sub.s is the thickness of the antenna layer. FIG. 5 shows a
two-dimensional view of an LC with two dye-zeolite antenna layers.
The number of antenna layers can be increased as desired, the sum
of the thicknesses of the antenna layers being much smaller than d.
The antenna layers may have different structures, for example
contain different dye-zeolite crystals. The designation of layer
thicknesses and refractive indices is analogous to FIG. 4.
[0018] This structure solves not only the problems (A) to (C)
detailed under "State of the art" but has a considerable influence
on the stability of the chromophores because the donor molecules
pass on the energy absorbed via near-field interaction in the
sub-picosecond range, such that barely any time remains for a
reaction in the electronically excited state, and because the
spatial delimitation by the nanotubes results in a cage effect,
thus making impossible or at least considerably hindering both
intra- and intermolecular movements which could lead to reactions.
More particularly, it is also possible to quantitatively exclude
small reactive molecules, for instance oxygen.
[0019] The incorporation of the dyes into the zeolite L crystals is
effected from the gas phase in the case of uncharged dye molecules,
and from a suitable solvent in the case of cationic dyes. Dyes
adsorbed on the outer zeolite crystal surface are subsequently
removed by washing with a solvent. The incorporation of different
dyes can be effected sequentially or in parallel. Sequential
incorporation results in defined dye domains, and the positioning
of the acceptor molecules in the middle of the zeolite channels may
be advantageous owing to the better screening from external
reactive species. For other end uses or for certain chromophores,
positioning at the ends of the channels gives rise to optimal
properties. The parallel incorporation of different dyes leads to
mixing within the crystal. To eliminate self-absorption,
irrespective of the incorporation process, a large donor/acceptor
ratio is selected, which is generally greater or considerably
greater than 10:1.
[0020] The application of the dye-laden zeolite crystals to a
substrate (for example glass) and the coating with a transparent
polymer can be implemented, for example, as follows: (1) By
production of a homogeneous mixture of polymer and zeolite crystals
in a suitable solvent. The mixture is applied to the substrate by
spreading (e.g. doctor-blading) or spin-coating. The evaporation of
the solvent gives rise to a robust zeolite-polymer layer of defined
thickness. (2) By production of one or more zeolite layers
(directed or unordered) on the substrate and subsequent fixing with
a little polymer. After the drying, the rest of the polymer layer
is applied by spreading (e.g. doctor-blading) or spin-coating. In
other cases, the method as illustrated in FIG. 3 may be
advantageous; on this subject see: Organizing supramolecular
functional dye-zeolite crystals, A. Zabala Ruiz, H. Li, G.
Calzaferri, Angew. Chem. Int. Ed., 2006, 45, 5282-5287; Fabrication
of oriented zeolite L monolayers employing luminescent
perylenediimide-bridged Si(OEt).sub.3 precursor as the covalent
linker, H. Li, Y. Wang, W. Zhang, B. Liu, G. Calzaferri, Chem.
Commun. 2007, 2853-2854; Fabrication of oriented zeolite L
monolayer via covalent molecular linkers, Y. Wang, H. Li, B. Liu,
Q. Gan, Q. Dong, G. Calzaferri, Z. Sun, J. Solid State Chemistry,
2008, 181, 2469-2472. The crystals may also be aligned similarly to
a nematic phase, in which case a considerably tighter packing than
that depicted in FIG. 3 (on the right) is possible. FIG. 3 shows an
electron micrograph on the left and a fluorescence micrograph on
the right, and originates from: Organisation and Solubilisation of
Zeolite L Crystals, Olivia Bossart and Gion Calzaferri, Chimia
2006, 60, 179-181.
[0021] In each case, if required, a covering material (for example
a glass plate or a polymer film) can be applied to the
zeolite-polymer layer. The relative position of the luminescent
zeolite-polymer layer is controlled by the thickness of substrate
and covering material. The covering material can be covered with a
further dye-zeolite layer by repetition of the above-described
procedure, which allows a structure as shown in FIG. 5 to be
achieved. The application of further dye-zeolite layers and
intermediate layers can be repeated as often as desired, which
allows defined stacks of antenna layers separated by intermediate
layers.
[0022] The structure of the iLC or of a luminescence disperser (LD)
(FIG. 8) is analogous to that of the LC (FIG. 1). Instead of the
receiver in the LC, an emitter is installed as excitation light
(e.g. UV). Total reflection transports the light through the light
conductor. When it hits a luminescent site, consisting of a
dye-zeolite crystal, the light is absorbed and emitted again. By
directed arrangement of the luminescent sites (dye-zeolite
crystals), the emission angle is selected such that the photon
leaves the light conductor (cf. FIG. 1, exiting light flux). The
body is transparent to wavelengths which enter the body and are not
absorbed by the luminescent sites (dye-zeolite crystals). By virtue
of the concentration distribution as a function of the emitter
distance and/or as a result of the reflection at the body sides, it
is possible to achieve homogeneous surface emission out of the body
(the last step partly approximates to the light boxes with diffuse
reflection in the box interior and an orifice through which the
light is emitted diffusely from the box). The wavelength range
within which the dye-zeolite nanocrystals used emit can be selected
by adjusting the donor/acceptor combination from narrow-band
emission to white light (on this subject see G. Calzaferri, S.
Huber, H. Maas, C. Minkowski Angew. Chem. Int. Ed. 42, 2003,
3732-3758; G. Calzaferri, K. Lutkouskaya, Photochem. Photobiol.
Sci., 2008, 7, 879-910).
BRIEF DESCRIPTION OF THE FIGURES
[0023] FIG. 1. Drawing of a conventional luminescence concentrator
(LC).
[0024] FIG. 2. Luminescent sites: cylindrical zeolite nanocrystals
with organized dye molecules, which function as donors (grey
rectangles) and acceptors (black rectangles).
[0025] FIG. 3. Oriented zeolite layer. On the left: electron
microscope image of cylindrical zeolite L crystals on a glass
substrate. On the right: the crystals may also be aligned similarly
to a nematic phase (electron microscope and fluorescence microscope
image).
[0026] FIG. 4. Luminescence concentrator with a dye-zeolite antenna
layer.
[0027] FIG. 5. Two-dimensional view of an LC with two dye-zeolite
antenna layers.
[0028] FIG. 6. Luminescence concentrator-tandem solar cell
apparatus.
[0029] FIG. 7. Combination of luminescence concentrator-solar cell
apparatus with hot water production.
[0030] FIG. 8. Reverse utilization of LC. Instead of the receiver,
an emitter is installed on the LC, and thus the LC is mutated to an
iLC. The emitter emits excitation light into the luminescence
disperser. The light is absorbed by the dye zeolite (luminescent
site) and emitted again as luminescence. By suitable arrangement of
luminescent sites, the luminescent emission can be directed such
that the light leaves the light conductor.
[0031] FIG. 9. LC using rare earth emitter antenna. The Ln.sup.3+
is fixed according to: SOMC@PMS. Surface Organometallic Chemistry
at Periodic Mesoporous Silica, R. Anwander, Chem. Mater. 2001, 13,
4419-4438.
[0032] FIG. 10. Pyrene as a donor and some possible ligands, as
examples (from left to right: pyrene, 2-carboxy-7-aminopyrene,
1-pyreneamine, 1-pyrenecarboxylic acid).
[0033] FIG. 11. This diagram shows how an image can be projected
onto the retina of the viewer (eye lens) instead of an object with
the aid of a surface with directed emission. Individual image
elements on the surface emit photons at the spatial emission angle
alpha. The emission angle of the individual image point determines
which pixel of the image to be projected has to be emitted by this
image point.
[0034] FIG. 12. Examples of cationic dyes which have been
incorporated into zeolite L and are options for the use described
here.
[0035] FIG. 13. Examples of uncharged dyes which have been
incorporated into zeolite L and which are options for the use
described here.
MODES FOR CARRYING OUT THE INVENTION
1. Building an LC
[0036] The incorporation of the dyes into the zeolite L crystals is
effected generally from the gas phase at elevated temperature in
the case of uncharged dye molecules, and from a suitable solvent in
the case of cationic dyes. Dyes adsorbed on the outer zeolite
crystal surface are subsequently removed by washing with a solvent.
The incorporation of different dyes can be effected sequentially or
in parallel. In the case of sequential incorporation, the result is
defined dye domains, in which case the positioning of the acceptor
molecules in the middle of the zeolite channels may be advantageous
owing to the better screening from external reactive species. The
parallel incorporation of different dyes leads to mixing within the
crystal. To eliminate self-absorption, a large donor/acceptor ratio
is selected (>10:1). Examples of dyes which have been
incorporated successfully into the channels of zeolite L in this
way are compiled in FIGS. 12 and 13.
[0037] The application of the dye-laden zeolite crystals to a
substrate (for example glass) and the coating with a transparent
polymer (e.g. PMMA, CR39, PVA) can be implemented, for example, as
follows: (1) By production of a homogeneous mixture of polymer and
zeolite crystals in a suitable solvent. The mixture is applied to
the substrate by spreading (e.g. doctor-blading) or spin-coating.
The evaporation of the solvent gives rise to a robust
zeolite-polymer layer of defined thickness. (2) By production of
one or more zeolite layers (directed or unordered) on the substrate
and subsequent fixing with a little amount of polymer. After
drying, the rest of the polymer layer is applied by spreading (e.g.
doctor-blading) or spin-coating. In other cases, the method as
illustrated in FIG. 3 may be advantageous; on this subject see:
Organizing supramolecular functional dye-zeolite crystals, A.
Zabala Ruiz, H. Li, G. Calzaferri, Angew. Chem. Int. Ed., 2006, 45,
5282-5287; Fabrication of oriented zeolite L monolayers employing
luminescent perylenediimide-bridged Si(OEt).sub.3 precursor as the
covalent linker, H. Li, Y. Wang, W. Zhang, B. Liu, G. Calzaferri,
Chem. Commun. 2007, 2853-2854; Fabrication of oriented zeolite L
monolayer via covalent molecular linkers, Y. Wang, H. Li, B. Liu,
Q. Gan, Q. Dong, G. Calzaferri, Z. Sun, J. Solid State Chemistry,
2008, in press. The crystals can also be aligned similarly to a
nematic phase, in which case a considerably tighter packing than
that depicted in FIG. 3 (to the right) is possible. FIG. 3 shows an
electron micrograph on the left and a florescence micrograph on the
right, and originates from: Organisation and Solubilisation of
Zeolite L Crystals, Olivia Bossart and Gion Calzaferri, Chimia
2006, 60, 179-181.
[0038] In each case, if required, a covering material (for example
a glass plate) can be applied to the zeolite-polymer layer. The
relative position of luminescent zeolite-polymer layer is
controlled by the thickness of substrate and covering material. The
covering material can be covered with a further dye-zeolite layer
by repeating the above-described procedure, which allows a
structure as shown in FIG. 5 to be achieved. The application of
further dye-zeolite layers and intermediate layers can be repeated
as often as desired, which allows defined stacks of antenna layers
separated by intermediate layers to be produced.
2. Production of an LC with Exploitation of Surface-Enhanced
Plasmon Resonance
[0039] The controlled enhancement of luminescent properties of
molecules by metal nanostructures (thin layers or particles) has
been known for a few years (K. Aslan, I. Gryczynski, J. Malicka, E.
Matveeva, J. R. Lakowicz, C. D. Geddes, Curr. Opin. Biotechnol. 16,
2005, 55). Studies regarding potential uses have concentrated to
date on the biotechnology and LED fields. Together with the novel
LCs described here, this gives rise to a series of innovative
options for use of metal-enhanced luminescence: disk-shaped zeolite
L crystals are first laden with donor molecules. The acceptor
molecules present in deficiency are incorporated subsequently and
are thus at the ends of the zeolite channels. The substrate
consists of a conventional carrier material (e.g. glass) which is
coated with a thin metal film. Thereafter, the disk-shaped,
dye-laden zeolite crystals are applied such that any direct contact
between the metallic substrate and the dyes is prevented. This is
accomplished by the above-described process to form an aligned
layer, which results in distances in the region of a few nanometers
between metal film and acceptor molecules. In the case of such
distances (direct contact between dye and metal film is not
required and must generally be avoided), the emission of the dyes
can be enhanced significantly by excitation of surface plasmons in
the metal film and the associated increase in the electromagnetic
field. With regard to the efficiency and stability of an LC, this
structure may bring the following advantages: (i) Shortening of the
lifetime of the excited state of the acceptor molecules and hence
an increase in the photostability. (ii) Increase in luminescent
quantum yield of the acceptor molecules and hence higher efficiency
of the LC. There is additionally the possibility of using acceptor
molecules which have a low quantum yield but have other
advantageous properties (stability, cost). The same effect leads to
enhanced absorption, but only in the region of a few nm removed
from the metal surface.
3. Building an LC Using Rare Earth Chromophores as Emitters
[0040] It is well known that rare earths Ln.sup.3+ can be
incorporated in different form into the channels of zeolite L and
lead to interesting luminescent properties (Luminescence properties
of nanozeolite L grafted with terbium organic complex, Y. Wang, H.
Li, W. Zhang, B. Liu, Materials Letters, 2008, 62, 3167-3170;
Highly Luminescent Host-Guest Systems Based on Zeolite L and
Lanthanide Complexes, Y. Wang, Z. Guo, H. Li, J. Rare Earth, 2007,
25, 283-285; Sensitized near infrared emission from
lanthanide-exchanged zeolites, A. Monguzzi, G. Macchi, F. Meinardi,
R. Tubino, M. Burger, G. Calzaferri, Appl. Phys. Lett. 92, 2008,
123301/1-123301/3).
[0041] Here, we use a new kind of combination of an antenna hybrid
material in which a rare earth ion serves as the emitter. The
special feature of this combination is that the rare earth
compounds--which have only comparatively low light absorption even
when they are equipped with antenna ligands--can be excited by
means of our antenna systems which have very high light absorption,
without losing their ability to emit in a narrow band, as explained
in FIGS. 9 and 10. It is also possible to use, as antenna
absorbers, molecules which have markedly nonlinear optical (NLO)
properties, such that it is possible to work with two-photon
excitation. Two-photon excitation antennas may be of high interest
for solar uses, but also for microscopy ranging as far as
diagnostics; on this subject see Cell-Permeant Cytoplasmic Blue
Fluorophores Optimized for In Vivo Two-Photon Microscopy With
Low-Power Excitation, A. Hayek, A. Grichine, T. Huault, C. Ricard,
F. Bolze, B. Van Der Sanden, J.-C. Vial, Y. Mely, A. Duperray, P.
L. Baldeck, J.-F. Nicoud, Microscopy Research and Technique 70,
2007, 880-885. We use, among other substances, pyrene derivatives
because they bring very good prerequisites for successful
sensitization of Eu.sup.3+. They have high absorption in the near
UV, and have high luminescent yields and inter-system crossing; on
this subject see: A. R. Horrocks, F. Wilkinson, Proc. Rpy. Soc. A.
306, 1968, 257-273. The coordination properties of pyrenes to
lanthanide ions can be adjusted efficiently with the aid of simple
synthesis (attachment of acid, ester, amide, amino groups and
others). Substituents in the 2 position are notable in that the
ligands fit better into the zeolite L channels. Eu.sup.3+-pyrene
complexes can thus also serve as peg molecules which have
comparatively very narrow-band emission. In a donor-acceptor
cascade as shown in FIG. 9, a donor-pyrene molecule (D) is
electronically excited by light absorption. It then transfers its
excitation energy radiationlessly via near-field interaction to
neighboring molecules until it arrives at a pyrene ligand
coordinated to Eu.sup.3+. From there, an emitting state of
Eu.sup.3+ is then occupied, which somewhat later emits a long-wave
photon. The corresponding ligand synthesis and coordination
chemistry is well known; on this subject see D. M. Connor, S. D.
Allen, D. M. Collard, C. L. Liotta, D. A. Schiraldi, J. Org. Chem.
1999, 64, 6888-6890; A. Musa, B. Sridharan, H. Lee, D. Lewiss
Mattern, J. Org. Chem. 1996, 61, 5481-5484; C. Yao, H.-B. Kraatz,
R. P. Steer, Photochem. Photobiol. Sci. 2005, 4, 191-199. The
absorption and luminescence spectra of Py, Py-NH.sub.2 and Py-COOH
are shown in FIG. 10. It can be inferred therefrom that Py can
serve very efficiently as a donor both for Py-NH.sub.2 and for
Py-COOH. Loading of zeolite L with subsequent installation of
Eu.sup.3+-pyrene complexes and production of LCs based on these
antennas leads to LCs with spectral properties of particular
interest from a performance point of view. Intrinsic absorption
becomes so low here that it can be neglected completely.
4. The Principles, Routes and Methods Described for the Building of
LCs Also Apply to the iLCs.
Commercial Utility
1. LCs for Collection and Concentration of Sunlight
[0042] The use of LCs is well known from the literature. With
regard to the principles in conventional use, there is at first no
difference between the LCs being addressed here and previously
described variants. However, the central difference is that the
problems with the LCs known to date, which are described under
"State of the art", have been solved or at least reduced to a
sufficient degree that they can now also be achieved for this use.
Owing to the new way in which they are constructed, these LCs and
the associated advantageous optical properties lead to a
considerably better cost/benefit ratio of building-integrated
photovoltaic systems and for collection and subsequent transport of
light, for example in a glass fiber.
2. LCs for Tandem Solar Cell
[0043] The principle is that light in the range from near UV up to
a wavelength limit which may, for example, be 600 nm is conducted
via LCs to a "large band gap" solar cell, and that a "small band
gap" solar cell on the reverse side of the LC collects the
long-wave portion of the light. This allows building of a tandem
solar cell which does not require "current matching" and in which
no complex layers are needed; see FIG. 6. This tandem arrangement
allows a maximum thermodynamic efficiency of somewhat more than 43%
compared to a maximum of 29% in a "single band gap" photovoltaic
cell; on this subject see Peter Wurfel, Physics of Solar Cells,
Wiley-VCH, Weinheim, 2005.
3. Photovoltaic-Hot Water Integration
[0044] Another possible use which becomes an option with partial
LCs is the integration of photovoltaics into a hot water production
system. This is an idea which is well known in principle. It
consists in utilizing the long-wave portion of the incident solar
radiation for hot water production and the shorter-wave portion to
operate a photovoltaic cell. This has huge energetic advantages and
can also contribute (in hot countries) to the cells not becoming
too hot (for example by virtue of a 60.degree. C. limit). By using
the novel LC devices described here, it is possible to physically
completely decouple the solar cell portion and the hot water
portion, as outlined in FIG. 7, and thus to solve the problems
which are a consequence of the combined large area of the two
transducers (thermal and electrical) and which lead in conventional
systems to hurdles which can barely be overcome in practical use.
The LC is transparent to infrared radiation over wide ranges,
especially in the near IR.
4. Inverted LC
[0045] The term luminescence concentrator might seem curious for
this "inverted device". Owing to the analogy to the physical
process, we wish nevertheless to use this name and to abbreviate it
to iLC. The structure of an iLC is such that light is fed in
laterally at one or more points, for example with the aid of an
LED. The light is then absorbed by dye-zeolite antennas and passed
on within the antenna system in an analogous manner to that in the
LC until it meets a region in which it is absorbed by a second type
of antenna crystals which are aligned such that the light is no
longer reflected internally but leaves the layer. This can make a
glass or plastic surface appear partially dark and partially as a
diffuse emitter. Areas of use for such iLCs are various, and range
from signaling systems, through illuminated signage, through room
lighting, flat/diffuse light sources and background
illumination.
[0046] One use consists in the possibility of implementing a visual
display unit via a two-photon emission process. By loading the
zeolites with a two-photon emission system, orthogonal incidence of
the two excitation wavelengths induces one or more pixels to
emission. The incident intensity of the excitation sources can be
used to regulate the brightness of the individual pixels. Suitable
emission wavelengths adjust the pixel color. Instead of diffuse
emission, it is also possible to establish directed emission with a
limited emission opening angle, in order to increase the emission
intensity in the desired direction.
5. LCs Exploiting Surface-Enhanced Plasmon Resonance
[0047] The phenomenon of surface-enhanced plasmon resonance (K.
Aslan, I. Gryczynski, J. Malicka, E. Matveeva, J. R. Lakowicz, C.
D. Geddes, Curr. Opin. Biotechnol. 16, 2005, 55) can be used in
conjunction with the structure shown in FIG. 4 in an ideal manner
to optimize the luminescent properties of the dyes. A thin metal
layer adjoining the antenna layer leads to an enhancement of
luminescence by molecules close to the interface between antenna
layer and metal layer. The use of an antenna layer consisting of
oriented zeolite L crystals (channels at right angles to the
surface of the metal film) allows the distance of the metal surface
from the acceptor or donor molecules to be controlled. This avoids
direct contact between the dye molecules and the metal surface. In
a conventional LC (consisting of dye molecules in a polymer layer)
and in all other LC designs known to date, such an optimization of
luminescent properties is not possible. In the concept that we have
developed, use of surface-enhanced plasmon resonance is of
particular interest for optimization of luminescent properties of
the acceptor molecules.
6. LCs Using Rare Earth Chromophores as Emitters
[0048] Here we propose a new combination of an antenna hybrid
material, in which a rare earth ion serves as an emitter. The
special feature of this combination is that the rare earth
compounds--which have only comparatively low light absorption even
when they are equipped with antenna ligands--can be excited by
means of our antenna systems which have very high light absorption
without losing their ability to emit in a narrow band, as explained
in FIGS. 9 and 10. (The spectra shown in FIG. 10 have been taken
from the literature: C. Yao, H.-B. Kraatz, R. P. Steer, Photochem.
Photobiol. Sci. 2005, 4, 191-199.) The antenna absorbers used may
also be molecules which have marked NLO properties, such that it is
possible to work with two-photon excitation. Two-photon excitation
antennas may be of high interest for use in solar technology, but
also for microscopy ranging as far as diagnostics (Cell-Permeant
Cytoplasmic Blue Fluorophores Optimized for In Vivo Two-Photon
Microscopy With Low-Power Excitation, A. Hayek, A. Grichine, T.
Huault, C. Ricard, F. Bolze, B. Van Der Sanden, J.-C. Vial, Y.
Mely, A. Duperray, P. L. Baldeck, J.-F. Nicoud, Microscopy Research
and Technique 70, 2007, 880-885).
7. LC Device for Use as a Scintillation Detector
[0049] DMPOPOP and other highly fluorescent dyes which are used in
scintillation counters for the measurement of ionizing radiation,
for instance gamma quanta, can be incorporated into zeolite L in
very high concentration, up to about 0.2 mol/l. They can pass on
their electronic excitation energy to acceptors. For DMPOPOP, for
example, it is possible to use PR149, DXP or oxonine as acceptors.
With the aid of such dye-zeolite L materials, it is possible to
build LCs as described in 1. to 3. and in FIGS. 4 and 5. Such LCs
are rendered reflective on the open sides and installed at a site
in the detector. It is thus also possible to collect extremely
sensitively ionizing radiation over a large area and convert it to
luminescence of the scintillator dye. This is transferred via
energy transfer to the acceptor, which then emits at a long
wavelength. Via total internal reflection, the luminescence to be
measured is transferred to the detector. It is particularly simple
and inexpensive in such a device to protect the detector from
incident ionizing radiation.
8. iLCs for Locally Directed Emission
[0050] Oriented dye-zeolite antennas allow the achievement of
directed emission (on this subject see especially G. Calzaferri, K.
Lutkouskaya, Photochem. Photobiol. Sci., 2008, 7, 879-910). Instead
of the viewing of a visual display unit, it is thus possible to
directly project images onto the retina of the eye, without
external optical elements. This is illustrated schematically in
FIG. 11: individual image points emit at a defined angle alpha(i).
Through the eye lens, this image point hits a particular site on
the retina. The emission angle alpha determines the point on the
retina at which the image point is depicted. By suitable
arrangement, it is thus possible to generate one image per eye. By
means of two corresponding images, a three-dimensional image can be
transmitted to the viewer. The opening angle of the emission cone
determines the pixel size on the retina and hence the sharpness of
the image.
9. LCs for the Implementation of an Eye Replacement Device
[0051] In the case of a very inadequate or missing eye lens, it is
possible to directly stimulate a functioning retina with a directed
emission matrix. For this purpose, the emission matrix is applied
very close to or directly to the retina, and the directed emission
is fed directly to the individual light receptors on the retina.
The image source can be generated externally by a camera or a
mini-camera in the eye. A synthetic eye apparatus has thus been
established. In the case of a poorly functioning retina, this
process can be used to increase the light source intensity, such
that the receptors respond to the enhanced light stimuli.
10. iLC Device for the Production of Spotlights
[0052] The directed emission can also be utilized to establish a
spotlight with a defined emission cone angle. In this case, the
emission elements should be arranged in parallel, with the same
emission cone opening angle.
* * * * *